Fujitsu M4000 User Manual download pdf (Page 53)

Chapter 2 System Features and Capabilities 2-9

■ Periodically performs memory patrol to detect memory software errors and

stuck-at faults, even in memory areas not normally used (Memory patrol).

Memory patrol prevents faulty areas from being used and thereby prevents the

occurrence of system failures.

■ Keeps checking the status of each component to detect signs of an imminent fault,

such as system down occurrences. Prevents system failures (Status checking of

components).

2.4.2 Availability

Availability represents the ratio of time the midrange server is accessible and usable.

An operating ratio is used as an index.

Faults cannot be completely eliminated. To provide high availability, the system must

be incorporated with mechanisms that enable continuous system operation even if a

failure occurs in hardware, such as components and devices, basic software such as

the operating system, or business application software.

The midrange servers can provide high availability by implementing the items listed

below. Also, a cluster configuration can provide higher availability.

■ Supporting redundant configurations and active replacement of power supplies

and fans.

■ Supporting redundant configurations, mirroring, and active replacement of disks.

■ Extending the range of automatic correction of temporary faults in memory,

system buses, and LSI internal data.

■ Support of an enhanced retry function and degradation function for detected

faults.

■ Shortening the downtime by using automatic system reboot.

■ Shortening the time taken for system startup.

■ XSCF collection of fault information, and preventive maintenance using different

types of warnings.

■ Supporting the extended error checking and control function in the memory

subsystem. The memory extended error checking and control function is an ECC

code that enables correction of data from a 4-bit nibble error caused when an

entire DRAM chip fails. This feature works for DIMMs employing x4 I/O DRAM.

■ Supporting the memory mirroring function enables normal data processing

through the other memory bus, thereby preventing system failures, in response to

a DIMM stuck fault in the same memory bus.

Since the memory patrol facility is implemented in hardware, it is not affected by the

software processing workload.

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Fujitsu M4000 User Manual Page 53